Even though she is not a founding member, I would definitely like to see Black Widow in there. She would fit in really good along with the SHIELD backdrop, as a secret agent. She could even be a recipient of a secondary attempt at the Super-Soldier Serum created during the Cold War (since the original was lost) thereby giving her some Super-hero chops (though not to the level as Cap). The serum could be said to slow her aging, making her a cold-war double agent from the 80s (end the Cold War) that is still kicking 35 years later. She could be already included as Fury is going about recruting IM, etc...

And Wasp is a must... She can be the first test subject for the Pym Particles, where the shrinking process creates residual biochemical energy that she can expend in her Wasp-sting blasts.

Along with that, I just hope that we don't see a guy with a horned helmut talking to ants. Leave that to Honey I Shrunk the Kids.